Silicon-based materials are important commercial materials. In particular, elemental silicon is a widely used semiconductor material for electronic and solar cell applications. The semiconducting properties and electron mobilities of silicon can be altered using dopants. The formation of semiconductor devices generally involves the formation of regions of the device with selectively doped silicon in which the dopants alter the electrical conduction properties or other desired properties. Through the selected doping process different domains of the device can be formed that provide functionalities for particular device to exploit the semiconductor properties, such as a diode junction formed with separate materials with a p-type dopant and an n-type dopant. For example, n-type dopants provide excess electrons that can populate the conduction bands, and the resulting materials are referred to as n-type semiconductors. P-type dopants provide electron deficiencies or holes and are used to form p-type semiconductors. Through appropriate doping, a wide range of devices can be formed, such as transistors, diodes and the like. Silicon oxides, silicon nitrides and silicon oxynitrides can be used as dielectric materials, and these materials can be particularly desirable for use along with silicon semiconductors for their compatibility and lack of metals that can migrate to a silicon semiconductor.
In general, processing costs are a significant consideration for commercial applications. It can be desirable to use printing approaches for moderate resolution applications since commercial printing equipment is available and processing costs can be reasonable. Screen printing is a widely used printing technique commercially. Screen printing is generally performed with a paste with a range of acceptable rheological properties consistent with the screen printer. Other commercially compatible deposition approached include, for example, inkjet printing, spin coating, spray coating, knife edge coating and the like.
The wide ranges of semiconductor applications generate commercial relevance for silicon materials in many forms. For example, the formation of large area thin film transistors or the like generates a demand for alternative semiconductor processing approaches. Also, with increasing energy costs and increasing demand for energy, the market for solar cells has been correspondingly increasing. A majority of commercial solar cells comprise photoconducting silicon semiconductors, and differential doping of the semiconductor facilitates harvesting of the photocurrent. Some solar cells have patterning of silicon doping for the formation of doped contacts along the horizontal plane of the device. Thin film silicon solar cells can have dopant variation in a vertical orientation relative to the plane of the device. With increasing performance demands, there are pressures to keep costs down so that improvements in material processing is very desirable as an approach to address performance issues while keeping costs at acceptable levels. Germanium is a semiconducting material that can be an alternative to silicon with similar semiconducting properties. Also, silicon and germanium can form semiconducting alloys with each other.